Plastometer



Nov. 8, 1955 H. R. RAsMussr-:N 2,722,832

PLASTOMETER Filed July 24, 1955 2 sheets-sheet 2 INVENTR. ra/Jj?. Hofs msse/z A T TOR/VE YS United States Patent fiice 2,722,832 Patented Nov. 8, 1955 PLAsToMETER Harald R. Rasmussen, Rumford, R. I., assignor to Scott Testers, Inc., a corporation of Rhode Island Application July 24, 1 953, Serial No. 370,149

4 Claims. (Cl. 73-101) This invention relates to improvements in arplastometer, particularly the plastometer disclosed in Patent No. 2,037,529, issued April i4, 1,936, to Melvin Mooney.

In the plastometer disclosed in the above patent the rotor through which the shearing action is applied to the specimen under test has a forked shaft which engages a key or spline in a vertical shaft to be rotated thereby. In conducting tests, certain of the material in the cavity of the die or test chamber leaks past the shaft of said rotor and accumulates in the rotor shaft bearing to a degree tending to raise the rotor within the test chamber, which action is undesirable. The drive for the vertical shaft comprises an 1800 R. P. M. motor driving an eighttooth pinion which engages with a ninety-tooth gear on the displaceable horizontal shaft, then through a single thread worm to an eighty-tooth worm wheel to produce the 2 R. P. M. required in the vertical shaft.` Such gear train and motor drive is undesirable in that considerable difficulty is had in aligning the gear vtrain in the original assembly but especially so when replaced in the field.

An object of this invention is to provide a rotor for an apparatus of the above type so constructed as to avoid any tendency of rising in the test chamber and to facilitate the ready cleansing thereof.

Another object of the invention is to provide a rotor with a shaft having a much larger bearing driving surface with the vertical shaft.

Another object of the invention is to provide a drive for the vertical shaft so arranged as to effect ease of original assembly and field maintenance.

Another object of the invention is to provide a drive for the vertical shaft which will be efficient, quiet, and have a long life.

With these and other objects in view, the invention consists of certain novel features of construction as will be more fully described and particularly pointed out in the appended claims.

In the accompanying drawings:

Figure 1 is a sectional view of a fragmental portion of a plastometer embodying my invention;

Figure 2 is a central sectional view of the upper and lower platen of the machine and showing on an enlarged scale the drive connection therebetween;

Figure 3 is a sectional View of the lower platen showing the rotor connection between the drive shafts thereof; and

Figure 4 is a sectional view in plan of the base of the apparatus and the driving gear train therefor.

The plastometer or apparatus for measuring the viscosity and elastic recovery of rubber and plastic materials generally according to the present invention has a vertical shaft which is hollow and provided at its upper end with a drive bushing having a square bore therethrough for receiving a similar square portion of the rotor shaft. The vertical shaft is journalled in ball bearings and driven through `a ,direct motor drive through a simple gear train which runs in an oil bath to assure both quiet and etlicient operation.

Referring to the drawings, particularly Figure l, 9 designates generally an apparatus of the type shown in the above patent to which reference ismade for a more detailed showing and description thereof. The apparatus, only so much of which is shown for a clear understanding of the present invention, comprises a base 10 having an upper side or wall 11 to which is secured the lower platen 12 which carries the lower die 13 (see Fig. 4). The lower platen 12 has a central circular recess 14, the bottom wall of which has a central bore 15. The lower die 13 is received in the recess 14 and has a reduced boss 16 through which a central bore 17 extends in register with the bore 15. The die is held in position by a die holder 18 which has a central bore 19 in which is received the boss 16 and is received in the recess 14 to rest against the die 13. Screws 20 secure the holder 18 in position. The bore 19 is of greater depth than the boss 16 and forms a circular chamber 21.

The upper die 13 is substantially similar to the lower die 13 and is similarly attached to the upper platen 12 which is also substantially similar to the platen` 12 and is movably mounted and supported from a superstructure 22 supported at the upper ends of vertical columns 23 rising from the wall 11. A manually operated lever 24 has a bifurcated end 25 which is secured to rotate with a shaft 26 journalled in bearings 27 which are guided for vertical movement in guide openings 28 formed in the side walls of the said superstructure 22. A spur gear 29 is received between the arms of the bifurcated end Z5 and is mounted on the shaft 26 to rotate therewith and with the lever 24. The spur gear engages with a toothed track or gear rack 30 which is held stationary. A yoke link 31.is attached at one end to the platen 12 as at 32, and the other or yoke end of the link straddles the arms of the bifurcated end 25 and is pivotally secured thereto as at 33 at a location so as to be eccentrically mounted with reference to the axis of rotationv ofthe shaft 26.

In Figure l the platen 12 is shown in full lines in the upper position thereof. Swinging the lever 24 in a counter-clockwise direction from the full line position to that shown in the dotted line position will lower the platen 12' to position the upper die 13' into register with the lower die 13 as seen in Figure 2, to form a closed cavity therebetween in which a sample or specimen to be measured will be held against relative movement by the roughened surface of the walls of the cavity and will be acted upon by a rotor to be hereinafter described.

A bearing housing 34 (see Fig. 2) is secured on the base 10 as by screws 34 and depends vertically from the under side of the upper wall 11 of the base. The housing is hollow as at 35 in which there is received a pair of ball bearings 36, 36 which are secured in position by frictional engagement against inner abutments formed by split resilient rings 37. A hollow vertical shaft 38 having an annular flange 39 at its upper end is journalled in said bearings 36, 36', and the said flange 39 engages against the upper side of the inner race of the bearing 36. The upper end of the bore through the shaft is enlarged as at 40 (see Fig. 3) and threaded as at 41. A drive bushing 42 has a threaded shank 43, a bore 44 therethrough which is reduced at the lower portion thereof as at 44 and made rectangular in cross section forming a shoulder 45 at the junction of the bore portion of larger diameter and the said rectangular p'ortion. The bushing 42 is received in the bore portion 4i), the shank 43 engaging with the portion 41 to secure the bushing in position to rotate with the shaft 38. The vertical shaft 38 extends beyond the lower end of the housing 34 and a thirty-tooth worm wheel 46 is secured .E thereto for rotation therewith by a spline fastening 47 and a nut fastening 48 (see Fig. 2).

The rotor 49 has a circular head 50 from which ex tends a cylindrical shank 51 reduced as at 52 forming a shoulder 53. The reduced portion 52 is made square in cross section and terminates in a pointed end. The shank 51 extends through the bore 17 and is received in the bore portion 44 with the shoulder 53 resting against the shoulder 45 and the square shank portion S2 is received in the square bore 44 to have driving relation therewith. A seal packing 54 encircles the shank 51 at the bore 17. Thus, the rotor is detachably mounted in the Vertical shaft 38 to be driven thereby.

The thirty-tooth gear 46 engages with a single thread worm 55 on a horizontal shaft 56 which is journalled in bearings 57, 58 on the base 10 (see Fig. 4). A fiftytooth spur gear 59 is mounted on the shaft 56 and engages with fifty-tooth spur gear 6@ having a wider face 60' and mounted on a drive shaft 61 which is journalled in bearing 62 and connected to the output shaft 63 of a 60 R. P. M. ratio motor 64. Thus, the vertical shaft 38 and the rotor attached thereto are rotated the required 2 R. P. M. The base 10 has a well 65 formed therein for containing lubricant and in which the spur gears are submerged and rotated therein.

The shaft 56 is additionally mounted for axial movement and the right end portion thereof (see Figure 4) is journalled in a ball bearing 66 in a slidable housing 67 mounted on a bracket 68 attached to the base 1G. The housing 67 carries a knife edge 69 which is engaged by the arm 7@ of a U-spring 71, the other arm 72 of which is held against movement on a bracket 73. Thus, the shaft 56 is resiliently biased or spring loaded against axial movement towards the right. A dial gauge 74 has its stem 75 extending into engagement against the left end of the shaft 56 whereby any axial movement of the shaft 56 will be indicated on the indicator.

In the operation of the plastometer, the sample to be measured is placed across the open lower die 13, and the upper die 13 is lowered in register with the lower die to force the sample in the cavities of the dies and about the head of the rotor which is equally spaced from the walls of the said cavities, the knife edge about the dies shearing any excess of the sample which may protrude beyond the dies. The motor is now set into motion to rotate the rotor as above pointed out, which will exert a shearing action on the sample held against movement in the cavity formed by the closed dies. The resistance of the specimen to deformation by the shearing action of the rotor develops a thrust in the shaft 56 tending to axially move the same to the right against the bias of spring 71. The axial movement of the shaft 56 is followed by the stem 75, and thus indicates the amount of movement in the said shaft 56.

I claim:

1. In a plastometer having a hollow stator in which a specimen is received to be measured, a rotor disposed within said stator, a rotatable shaft for said rotor having an axial bore, a separate bushing detachably received in said bore at one end of the shaft for rotation therewith and having an axial opening therethrough non-circular in cross section and opening into said bore, said rotor having a shank portion non-circular in cross section and extending into said non-circular opening and of a size to engage the walls thereof for detachably securing the said rotor to said shaft for driving relation therewith, said bore extending all the way through said shaft whereby portions of said specimen leaking from said stator past said shank and into said bore will pass out thereof, and means for rotating said shaft.

2. In a plastometer as set forth in claim 1 wherein said non-circular opening and said non-circular shank are rectangular in cross section.

3. In a plastometer as set forth in claim l wherein said shank portion projects beyond the bushing inwardly of the shaft.

4. In a plastometer as set forth in claim 1 wherein Said shank is sealed against leakage from said stator past said shank.

References Cited in the file of this patent UNITED STATES PATENTS 1,966,246 Jackson July 10, 1934 2,037,529 Mooney Apr. 14, 1936 2,319,208 Clark May 18, 1943 2,614,405 Clausen Oct. 21, 1952 

